1. Field of the Invention
The present invention relates to an electrical part including an operating shaft and an operating member mounted to the operating shaft, which can suitably be formed by caulking the operating member to the operating shaft protruding externally from a housing of the electrical part.
2. Description of the Related Art
Such an electrical part is described by taking as an example a rotary sensor, which has been disclosed by the applicant. The rotary sensor is mounted to a vehicle or the like in order to detect, for example, the height of the vehicle. As shown in FIG. 7, such a rotary sensor has a bearing 2 which is mounted in a housing. An operating shaft 23 is rotatably inserted into the bearing 2, and has an operating portion 23a protruding towards the front from one end of the housing 1. The outside diameter of an end of the operating portion 23a is made slightly smaller to form an oblong flat portion 23b, formed by cutting, at the smaller outer diameter portion. An externally threaded portion 23c, which is threaded along its outer periphery, is formed at the upper portion of the flat portion 23b.
A lever, being a plate-like operating member 4, or the like is inserted into the flat portion 23b. From above the lever, a washer 6 for preventing loosening is inserted onto the externally threaded portion 23c to fasten a nut 5 onto the externally-threaded portion 23c, whereby the operating member 4 is mounted to the operating shaft 23 so as not to rotate.
A sliding element bearing 7 is mounted to a sliding element bearing mounting portion 23d at the other end of the operating shaft 23 which is disposed in the housing 1, so that it does not get dismounted from the sliding element bearing mounting portion 23d.
A sliding element piece 8 is mounted to the sliding element bearing 7. A holder 10 having mounted thereto an insulating base 9 with a resistance pattern is mounted to the housing 1 so as to oppose the sliding element piece 8.
The back side of the holder 10 is filled with a filler 13 in order to seal the rear side of the housing 1. On the other hand, a sealant 14 is forced into the front side of the housing 1 in order to seal the front side of the housing 1. Accordingly, the front and back sides of the housing 1 are sealed to prevent entry of foreign material, such as dirt, into the housing 1.
Such a conventional rotary sensor, or electrical part, is constructed by securing and mounting the operating member 4 to the operating shaft 23 with a nut or the like. Therefore, a washer 6 for preventing loosening of a nut 5 needs to be inserted onto the threaded portion 23c, and time is required to fasten the nut 5. As a result, the electrical part cannot be assembled with high efficiency.
In addition, parts, such as a nut 5 or a washer 6, are needed to mount the operating member 4 to the operating shaft 23, thereby increasing the number of parts used, which results in higher costs.
When the operating member 4 is mounted to the operating shaft 23 by fastening them together with a nut 5 or the like, the electrical part is made taller in correspondence with the height H of the nut 5, thereby preventing size reduction of the electrical part.
Such problems can be overcome if the operating member 4 can be caulked to the operating member 23 by one punching operation by a jig (not shown) or the like, wherein a load W can be produced, while the operating shaft 23 is incorporated in the housing of the electrical part. When such a method is used, time does not have to be used to assemble the electrical part using screws or the like, thereby increasing the efficiency with which the assembly can be performed. In addition, it becomes unnecessary to use parts, such as a screw 5 or a washer 6, thereby decreasing the number of parts, which makes the electrical part cheaper to produce. Further, since a nut 6 or the like do not have to be used, the height of the electrical part can be kept small, thus allowing size reduction of the electrical part.
When an attempt is made to caulk the operating member 4 to the operating shaft 23 incorporated in the housing of the electrical part, or rotary sensor, the sliding element mounting portion 23d at the other side of the operating shaft 23, which is in the housing, is suspended in mid-air in the housing 1, as shown in FIG. 7, so that when a load W is exerted onto the other end 23e of the operating shaft 23, as shown in FIG. 8, a force which tries to move the operating shaft rearward acts thereon. As a result, the operating portion 23 of the operating shaft 23 tries to push the bearing 2 in the housing 1 rearward, which breaks the internal portion of the housing 1 which supports the bearing 2.
Such a problem can be overcome by forming a load receiving portion 10a which protrudes from the center of the holder 10, such that it contacts the sliding element bearing mounting portion 23d of the operating shaft 23, as shown in FIG. 8. In such a case, even when a load W is exerted on the end 23e of the operating portion 23a, the operating shaft 23 does not move downward. Thus, the internal portion in the housing 1 does not break, even when the operating shaft 23 is caulked to the operating member 4.
However, since the load receiving portion 10a and the end 23d are always in contact with each other, rotation of the operating shaft 23 produces frictional torque at the load receiving portion 10a and the end 23d, causing the rotational torque of the operating shaft 23 to become unstable, or powder to be produced at the end 23d as a result friction. The powder sticks onto a resistance pattern surface of the insulating base 9, and cuts the sliding element piece 8, resulting in poor performance of the rotary sensor, or the electrical part.
The problem of unstable rotational torque of the operating shaft 23 can be overcome by forming a through hole (not shown) in the load receiver portion 10a of the holder 10, and inserting a jig of about the same outside diameter as that of the sliding element bearing mounting portion 23d of the operating shaft into the through hole. The jig is brought into contact with the sliding element bearing mounting portion 23d to caulk the end 23e of the operating portion 23a to the operating member 4. In such a method, the load W produced by caulking can be exerted on the jig, so that the performance of the rotary sensor is not affected. However, the through hole in the holder 10 of the rotary sensor admits a filler 13, being filled into the back side of the holder 10, into the housing 1.
An attempt has been made to overcome the problem of admittance of filler 13 by opening a through hole, not only in the holder 10, but also in the filler 13 after it has solidified. However, such a method prevents proper sealing of the housing 1, so that dirt or the like enters into the housing 1 from the through hole, making it unsuitable as a method to be used in producing a rotary sensor or the like.
As can be understood from the foregoing description, there are various problems when the operating member is caulked, while the operating shaft 23 is incorporated in the housing of the rotary sensor, or the electrical part. Therefore, in conventional electrical parts, an operating member 4 is caulked to a single operating shaft 23, as shown in FIG. 9, for incorporation in the electrical part, or rotary sensor.
Levers, or operating members 4, are formed into difference shapes and sizes according to the convenience of the customers. Therefore, when an operating member 4 is caulked to a single operating shaft 23, as mentioned above, each time the customer changes, the efficiency with which the electrical part is assembled is reduced.
An attempt has been made to overcome such a problem by previously caulking the variety of operating members 4 to the operating shafts 23 and storing the operating members 4 caulked to the operating shafts 23 as semi-manufactured products. However, the use of such a method increases storage costs, thereby increasing the cost of electrical parts.